uniquely, provides for an obligation to make a choice between a iure soli acquired German citizenship and another citizenship acquired iure sanguinis.

Many of the option rights granted to different categories of persons are limited in time: the option right has to be used within a certain period of time. This is completely understandable, for example, for the cases where children or young adults have an option right to acquire the citizenship of a parent or to reacquire a citizenship lost by them during their minority. Such a limitation is less understandable in cases where the option right is granted because the person has lived her or his whole life, or at least a considerable period thereof, in the country of residence and has therefore built up close ties with this country. These ties become closer and closer if somebody continues to live in the country involved. A limitation of this category of option rights is therefore, in principle, not justified.

An age limitation of these option rights can only be defended if it is likely that persons would wish to postpone the exercise of the option right until a moment, where one does not need to fulfil certain obligations. In the past, this could happen in almost all countries in respect of military service obligations.

Finally, with respect to stateless persons born on the territory of a state, we observed that while in many countries these persons acquire the citizenship of the country of birth ex lege, in several other countries they have option rights. The choice for an option right construction is as such in conformity with leading international instruments (1961 Convention and the ECN), but leaves the child for a considerable period without citizenship. This is problematic in view of Convention on the Rights of the Child (Art. 7) and of the Universal declaration of Human Rights (Art. 15). There are also a few countries, notably Malta, Norway, Romania and Switzerland, without explicit provisions on the acquisition of citizenship for persons (other than foundlings) born in a country who would otherwise be stateless. Whereas some critical review by states is justified, as to whether these persons really do not have access to another citizenship, the importance of birthright citizenship, as signalled at the outset of this paper, makes it difficult to justify the exclusion from citizenship of persons who fall through the mazes of the international system of citizenship laws.